The present invention relates to a method of and apparatus for measuring and aligning a rotary cylindrical or other rotationally symmetrical apparatus, e.g. in the form of a truncated cone. The rotationally symmetrical apparatus can be e.g. a kiln, such as a lime kiln or a cement kiln, or a drum, used in the chemical pulp industry.
Aligning a rotary cylindrical apparatus, such as a kiln or a drum, refers in this connection to straightening of the shell thereof, e.g. in order to keep the bricks in place in the kiln and for ensuring the desired functioning. In practice this means transferring the center points of the shell of a rotary object to a common straight line at the location of its supporting points. Adjustment of a rotary apparatus, in its turn, commonly refers to changing the declination angles of the support rollers of the rotary apparatus in respect of the center line of the apparatus. The adjustment aims at decreasing the wearing of mechanical parts and at desired functioning of the apparatus.
It is known from the state of art to align a rotary apparatus using e.g. the arrangement of FI utility model 8330 comprising i.a. orientation points fixed around the apparatus, measurement points fixed in connection with the support rings, measurement points fixed in connection with support rollers meant for supporting the support rings and at least two station points for setting the measuring device to said station point, and further apparatuses. Thus, the solution according to said publication utilizes, in addition to a measuring device, also a measurement point physically fixed in the object of measurement. The measurement point can be e.g. a target, an adhesive, a prism or a bar. In the solution according to said publication the object is measured when it is cold.
U.S. Pat. No. 5,491,553, in turn, presents an arrangement for measuring a kiln where the measuring device is fixed on a base that is located under the kiln for the measurement. The measuring device in the publication comprise three semiconductor lasers.
In the prior art solutions, such as e.g. in publication FI 8330, a drum-like object is measured stationary, i.e. cold. However, measuring of a cold kiln or drum does not give a right result, but the geometry of the kiln or drum changes during operation due to e.g. thermal expansion. In prior art, the thermal expansion is not always taken into account at all, but aligning is performed in accordance with the geometry of a cold kiln or drum. Then the alignment may differ even remarkably from the correct alignment. Further, taking thermal expansion into account during aligning is very troublesome and it is usually impossible to perform it exactly. And, a problem that arises in measuring a cold kiln or drum is that during the measurement and aligning the kiln or drum has to be kept out of operation. In practice this means that the measurement and aligning are to be performed during shutdown, when many repair and maintenance operations are performed at the mill. Scheduling the measurement and aligning with the other operations can be very difficult.
Another problem in the known solutions is caused by the aim to align the shell of the apparatus in a so-called indirect way, e.g., by measuring for instance the diameters of the support rollers, the distance between the support rollers, the diameter of the support rings, relative differences in altitude of the bases of the support rollers, the clearances of the casing and support ring etc. Such an indirect cold measuring is clearly more unreliable than measuring during the operation of the kiln, because the temperatures vary at different piers. For this reason, the clearance between the shell and the ring does not remain the same, but the center line of the kiln changes. According to prior art, the clearance is measured through backward slip, but the measurement is not totally reliable, as the slip changes a bit due to e.g. rotational speed.
In the solution according to said US-publication, locating the measuring device below the object to be measured is troublesome and time consuming. Additionally, the equipment that is needed is weighty. For these reasons, the measurement is carried out on one side of the support ring only. Further, the measurement is carried out below the shell on one side only, whereby it is not even possible to effect the measurement in close vicinity of the support ring because of the support rollers located below the support ring. An additional problem in the technique according to said US-publication is the narrowness of the sector on which the measurement points can be measured. A narrow measuring sector gives an unreliable result. Further, the shape of the shell changes the least on the lower side, which further increases the unreliability of the measuring result.